In-situ formed spinal implant

ABSTRACT

An in-situ formed spinal implant is provided, including an elongate strip having a proximal end and an opposite distal end, the strip having a plurality of spaced teeth disposed along edges of the strip. The strip has a generally arcuate or concave cross-section and is configured for being coiled into a spiral from the proximate end to the distal end for placement between adjacent spinal vertebrae, such that upon formation of the coiled shape, the teeth on a first edge engage one of the vertebrae, and teeth of an opposite, second edge engage the other of the vertebrae.

RELATED APPLICATIONS

This application is a divisional of, and claims 35 USC 120 priority fromU.S. Ser. No. 13/758,020, filed Feb. 4, 2013 and also priority under 35USC 119(e) base on U.S. Provisional Application Ser. No. 61/595,091filed Feb. 5, 2012.

BACKGROUND

The present invention relates generally to the field of spinal fusion orarthrodesis, as well as fracture repairs in cases of trauma orosteoporosis, and prosthetic replacement of a spinal joint, particularlyrelating to installation of a spinal repair device or system of suchdevices through minimally invasive methods.

Conventional spinal repair devices require an open installationprocedure, which increases patient recovery times and increases tissuedisruption at and around the incision site. In the case of spinal fusionor arthrodesis, the surgeon typically uses a “cage”, spacer, or aninterbody device that distracts the disc space to normal heights. Theconventional device aids in fusion of the vertebral bodies by providingan area within the device that can be packed with bone or artificialmaterial creating scaffolding for bone growth. The surgical site isopened sufficiently to allow for preparation of the disc and vertebralbodies, and to allow implantation of the device.

One drawback of conventional devices of this type is that in order toincrease stability, the device must be sufficiently sized in order tomaximize bone contact area or endplate coverage of the vertebral bodies.It is also desired that the frontal area of the device is minimized inorder to reduce the size of the incision. Since the devices are usuallyrectangular, trapezoidal, or cylindrical in shape, and the height isdetermined by the desired disc height of the patient, devices with alarger frontal area must be used in order to maximize bone contact area,requiring the surgeon to create a larger incision in order to installthe device.

Conventional devices also have varying tooth profiles or orientationsensitive geometry that helps prevent expulsion of the device whilefusion takes place. This geometry is typically oriented such that thetooth profile doesn't interfere with the installation of the device, andwill reduce the possible expulsion of the device when forces areapplied. This requires the surgeon to place the device in a specificlocation on the body such that the orientation of the device isaccomplished for preventing expulsion.

To those persons skilled in the art, the features, elements, and objectsof the present spine repair device will become apparent after readingthe details as described below.

SUMMARY

The above-identified needs are met by the present implant, which ispreferably delivered or installed thru a small cannula and deployedpercutaneously such that it has greater bone contact area thanconventional devices, small frontal area for smaller incisions,omni-directional tooth profiles for preventing expulsion, and anincreased height from its pre-deployed state. It is contemplated thatthe present implant and alternate embodiments are manufactured frommaterials such as polyetheretherketone (PEEK), titanium alloy, carbonfiber, or stainless steel. It is also contemplated that alternateembodiments of the present implant and alternate systems aremanufactured from shape memory alloys and shape memory polymers allowingthe device to conform more closely to the anatomical shape of the body.

The present implant or system of devices can be delivered through asmall diameter cannula and deployed intradiscal for use as an interbodyfusion device, deployed within the cancellous portion of the fracturedvertebral body in order to repair vertebral compression fractures, andas a reduced invasive disc replacement when used in conjunction withalternate systems of the present implant. Systems of the present implantinclude implantable fusion devices of varying length and heights for usein fusion, systems of various heights and sizes and materials for use injoint prosthesis, and systems that allow the delivery of natural orartificial materials for use in filling a void within a joint. Thesystem also includes instrumentation to deliver the implant or system ofdevices.

More specifically, an in-situ formed spinal implant is provided,including an elongate strip having a proximal end and an opposite distalend, the strip having a plurality of spaced teeth disposed along edgesof the strip. The strip has a generally arcuate or concave cross-sectionand is configured for being coiled into a spiral from the proximate endto the distal end for placement between adjacent spinal vertebrae, suchthat upon formation of the coiled shape, the teeth on a first edgeengage one of the vertebrae, and teeth of an opposite, second edgeengage the other of the vertebrae.

In another embodiment, a device is provided for installing a coiledelongate strip as a spinal implant. The device includes a housing havinga delivery tube at one end, and an implant loading chamber at anopposite end. A trigger-operated indexing mechanism associated with thehousing moves the strip from the loading chamber to the delivery tube. Adeployment tip is disposed at an end of the delivery tube, thedeployment tip including a flared ramp for changing the concavity of thestrip. A tensioning cord is disposed at the deployment tip and forms aloop for causing the strip to form a coiled spiral upon progressivemovement from the delivery tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a prior art cage;

FIG. 2 is a front plan view of the prior art cage of FIG. 1;

FIG. 3 is a top plan view of the prior art cage of FIG. 1;

FIG. 4 is a side plan view of the prior art cage of FIG. 1;

FIG. 4A is a horizontal cross-section taken along the line A-A of FIG. 4and in the direction generally indicated;

FIG. 5 is an isometric view of the present implant post-deployment;

FIG. 6 is a front plan view of the present implant post-deployment;

FIG. 7 is a side view of the present implant post-deployment;

FIG. 8 is a top plan view of the present implant post-deployment;

FIG. 8A is a vertical cross-section taken along the line A-A of FIG. 8and in the direction indicated generally;

FIG. 9 is an isometric view of an alternate embodiment of the presentimplant post-deployment;

FIG. 10 is a front plan view of the present implant post-deployment;

FIG. 10A is a horizontal cross-section taken along the line B-B of FIG.10 and in the direction indicated generally;

FIG. 11A is partial isometric view of an alternate contemplated toothprofile shape of the present implant shown in a partially flexedposition;

FIG. 11B is partial isometric view of another alternate contemplatedtooth profile shape of the present implant shown in a partially flexedposition;

FIG. 11C is partial isometric view of still another alternatecontemplated tooth profile shape of the present implant shown in apartially flexed position;

FIG. 12 is front plan view of an alternate embodiment of the presentimplant post-deployment;

FIG. 13 is side plan view of the present implant situated intradiscalpost-deployment;

FIG. 14 is top plan view of the present implant situated intradiscalpost-deployment;

FIG. 15A is top plan view of an alternate contemplated embodiment of thepresent implant situated intradiscal post-deployment;

FIG. 15B is top plan view of an alternate contemplated embodiment of thepresent implant situated intradiscal post-deployment;

FIG. 15C is top plan view of an alternate contemplated embodiment of thepresent implant situated intradiscal post-deployment;

FIG. 15D is top plan view of an alternate contemplated embodiment of thepresent implant situated intradiscal post-deployment;

FIG. 16 is a side plan view of the present implant pre-deployment;

FIG. 17 is a front plan view of the present implant pre-deployment;

FIG. 17A is a horizontal cross-section taken along the line A-A of FIG.17 and in the direction indicated generally;

FIG. 17B is an enlarged fragmentary horizontal cross-section taken alongthe line A-A of FIG. 17 and in the direction indicated generally;

FIG. 17C is an enlarged vertical cross-section taken along the line B-Bof FIG. 17 and in the direction indicated generally;

FIG. 17D is an enlarged vertical cross-section taken along the line C-Cof FIG. 16 and in the direction indicated generally;

FIG. 18 is an isometric view of the present implant pre-deployment;

FIG. 19 is an enlarged fragmentary side view of the distal end of thepresent implant pre-deployment;

FIG. 20 is an enlarged isometric view of the proximal end of the presentimplant pre-deployment;

FIG. 21 is an enlarged isometric view of the distal end of the presentimplant pre-deployment;

FIG. 22 is an enlarged vertical cross-section taken along the line B-Bof FIG. 17 and in the direction indicated generally;

FIG. 23 is an enlarged fragmentary side view of the present implantpre-deployment;

FIG. 23A is an isometric view of the present implant post-deployment;

FIG. 23B is an enlarged side plan view of an alternate contemplatedembodiment of the present implant pre-deployment;

FIG. 23C is an isometric view of an alternate contemplated embodiment ofthe present implant post-deployment; [graph]

FIG. 23D is an isometric view of an alternate contemplated embodiment ofthe present implant post-deployment; [iso of implant]

FIG. 24 is an enlarged side view of an alternate contemplated embodimentof the present implant pre-deployment;

FIG. 25 is an isometric view of the present implant delivery device;

FIG. 26 is a front plan view of the present implant delivery device;

FIG. 27 is an isometric view of the present implant delivery device;

FIG. 28 is an enlarged isometric view of the distal end of the implantdelivery device;

FIG. 29 is a front plan view of the implant delivery device of FIG. 25with components removed for clarity;

FIG. 29A is a cross section taken along the line D-D of FIG. 25 in thedirection indicated generally with components removed for clarity of theimplant delivery device;

FIG. 30 is an enlarged vertical cross-section of the distal end of theimplant delivery device;

FIG. 31 is a vertical cross-section of the implant delivery device.

FIG. 32 is an isometric view of the implant delivery device of FIG. 25with components removed for clarity; and

FIG. 32A is a bottom plan view of the implant delivery device of FIG. 25with components removed for clarity of the implant delivery device.

DETAILED DESCRIPTION

Referring to FIGS. 1-4A, a prior art implant is shown and generallydesignated 10, particularly designed for use as in spinal fusion orarthrodesis. However, it is contemplated that the present implant issuitable for use with other types of surgical procedures including,vertebral compression fractures, and as a minimally invasive discreplacement, or the like. The device 10 is preferably machined from barstock; however other fabrication techniques are contemplated includinginjection molding. The materials used to manufacture the device 10include polyetheretherketone (PEEK), titanium alloy, ceramic, bone,carbon fiber, or stainless steel, as is known in the art.

More specifically, the prior art implant 10 typically includes six sidesand an opening defining a passage 12 between upper and lower surfaces,respectively 13 and 14. The passage 12 is generally packed with bone orother natural or artificial materials for use in promoting fusionbetween an upper and lower vertebral body. At least one end 15 has areduced frontal area as defined by dimensions 16 and 17 and a radiusededge 18, and is provided for ease of insertion. As is known in the art,the upper surface 13 and lower surface 14 are usually populated withgeometry or teeth 19 used to increase pressure on the endplate of thevertebral body and prevent expulsion. A portion of at least one of thesurfaces 13 and 14 is formed flat or on a lordotic angle, in order tomore anatomically conform to the endplate of the vertebral body. Thelower surface 14 is sized to match the height as required by theanatomical disc height of the patient, and area as defined by dimensions11 and 17 is increased in order to enhance stability of the spinalcolumn.

Referring now to FIGS. 5-10A, the present implant in the post-deployedstate is generally designated 20. A main difference between the implants10 and 20 is that, instead of a solid shape, the present implant 20 isfabricated of an elongate strip formed into a thin walled spiral 22wound such that it forms a generally cylindrical shape with a passage 24located at the centroid or vertical axis of the spiral 22. The presentimplant 20 is configured for deployment in such a manner that both thepassage 24 and a diametrical dimension 25 can be controlled and moreclosely matched with the anatomical features of the patient. A lowersurface or first edge 26, and an upper surface or second edge 28 arepopulated with geometry or teeth 30 used to increase pressure on theendplate of the vertebral body and prevent expulsion. Walls 32 areconcave and nest within each other to provide greater stability of theimplant 20. It is contemplated that symmetric and asymmetric curved andsegmented shapes, both regular and irregular, are suitable for the walls32.

An opening 34 is preferably cylindrical or circular in horizontalcross-section, but it is contemplated that other shapes are alsosuitable, including but not limited to oval, triangular, square,pentagonal, hexagonal and other configurations of polygonal shapes, bothregular and irregular. The opening 34 is used post-deployment in orderto introduce bone or other natural or artificial materials into thepassage 24, and is formed by a linearly spaced plurality of holesdisposed along wall 32 of the elongate strip 20. In otherconfigurations, multiple openings can be located along the wall 32 toprovide access to the passage 24.

While other materials are contemplated, is preferred that the presentimplant 20 is manufactured from materials such as polyetheretherketone(PEEK), titanium alloy, carbon fiber, or stainless steel. It is alsocontemplated that alternate embodiments of the present implant andalternate systems are manufactured from shape memory alloys and shapememory polymers allowing the device to conform more closely to theanatomical shape of the body. For non-metallic or ferrous materials,radio-opaque stripes are placed along the length of the pre-deployeddevice to provide the surgeon feedback regarding the amount of implantcurrently deployed.

FIGS. 11A, 11B, and 11C are examples of alternate contemplated toothprofile shapes of the present implant, generally designated 20A, 20B,20C, shown in a partially flexed position. In the preferred embodiment,the upper and lower tooth profiles 40 and 41 respectively, are teethseparated by semi-circular tooth pockets and can be formed such that thecenter points of the upper and lower tooth profiles are aligned oroffset and staggered from each other. The tooth profile described abovewherein alternate embodiments are provided with upper and lowersymmetrical saw tooth shapes 42 and 43 which form a “v”-shaped toothpocket or notch that is triangular in shape, or of upper and lowerangled saw tooth shapes 44 and 45, or any combination thereof.

FIG. 12 is an alternate embodiment of the present implant, generallydesignated 60 post-deployment. Components shared with the presentimplant 20 are designated with the identical reference numbers. Thelower surface 26 and upper surface 28 are populated with geometry orteeth 30 used to increase pressure on the endplate of the vertebral bodyand prevent expulsion. It is contemplated that symmetric and asymmetricconvex and segmented profiles 61 about a horizontal centerline 62 ofsurfaces 26 and 28 are also suitable for providing desired anatomicalshapes, both regular and irregular.

The walls 32 of the implant 60 are concave and nest within each otherfor providing greater stability of the implant. It is also contemplatedthat symmetric and asymmetric curved and segmented wall shapes 32 abouta vertical or axial centerline 63 are also suitable, both regular andirregular.

FIGS. 13 and 14 depict the present implant 20 post-deployment within adisc space 70 of the vertebral bodies 72 and 74. FIGS. 15A thru 15D arealternate embodiments of the present implant 20 formed into varioussuitable configurations of the spiral 22, when viewed from above,including but not limited to oval, triangular, square, pentagonal,hexagonal, cardioid, and other configurations of polygonal shapes, bothregular and irregular. A transverse area of coverage depends on thechosen length of the pre-deployed implant 20, and how the implant isdeployed. The surgeon can deploy the implant 20 in such a manner thatboth the passage 24 and the diameter 25 can be controlled and moreclosely matched with the anatomical features of the individual patient.

FIGS. 16 thru 23D illustrate various aspects of the pre-deployedimplant, generally designated as 100. The pre-deployed implant 100 is anelongate strip that is generally cylindrical in shape as depicted incross sectional FIG. 17C, but it is contemplated that othercross-sectional shapes are also suitable, including but not limited tooval, triangular, square, pentagonal, hexagonal and other configurationsof polygonal shapes, both regular and irregular. Bend relief formationsor cutouts 102 are spaced along the length of the strip and will bedescribed in greater detail below. Edges of the strip are provided withlinearly spaced teeth 103 in the form of circular cutouts.

A break or slit 104 (FIGS. 17C, 17D) in the implant wall 106 causes thewall to transition from the main cylindrical shape defined by the wall106 to alternate shapes 106 a and 106 b (shown in phantom in FIG. 22) asthe implant 100 is wrapped around itself to form the spiral shape 22.This is achieved by bending an exterior of the wall 106 around an axis“A” perpendicular to a vertical axis “V” of the cylinder defined by thewall 106 and as depicted in FIG. 22. An interior surface 112 of the wall106 as shown in FIG. 22 becomes the exterior wall 115 of the implant 20as shown in FIG. 8A when fully deployed. The exterior surface 110 of thewall 106 becomes the interior wall 114 of the implant as depicted inFIG. 8A when fully deployed Implants of various heights can be providedby varying the amount of material removed from the cylindrical wall 106to create the break or slit 104, depending on the desired final deployedheight of the implant 20, 100. A larger break 104, meaning more materialremoved, will form a lower profile or shorter vertical deployed implant20 that distracts the disc space 70, and a smaller break 104 will form ahigher profile or taller vertical deployed implant that distracts thedisc space as illustrated in FIG. 13. In use, the surgeon will beprovided with a variety of implants 20, having different lengths and/orslit sizes.

A distal end 116 (FIG. 18) of the implant 100 is generally tapered on anangle cut perpendicular to the axis V of the implant. An oppositeproximal end 118 (FIG. 18) generally defines the geometry of the desiredfinal outer implant shape as depicted in FIGS. 15A thru 15D and isstiffer, in general, than the rest of the implant 100. This increasedstiffness begins after an angular transition 120 located perpendicularto the axis “V” that transitions to a smaller cross sectional area by anincreased break or slit 104 as shown in FIG. 17D. The preferredembodiment between the distal transition 120 and the proximal end 118 ofthe implant 100 has a generally thicker wall thickness “T” that isgenerally greater in size than the nominal implant wall thickness, thusproviding a stiffer cross sectional area.

It is also contemplated that the present implant 100 is constructedusing shape memory polymers or alloys, as is known in the art. In thepreferred embodiment, the present implant 100 maintains a constant wallthickness “T” throughout the entire length from the proximal end 118 tothe distal end 116, and the relative shapes and stiffness of portions ofthe implant are obtained thru the implant deployment process. Theprocess of bending the implant 100 around itself and turning theinterior surface 112 towards the exterior of the implant causes itsoriginal shape to form alternate shapes 106 a and 106 b, providing anactivation force for the shape memory materials.

Preferred tooth profile shapes defined by the teeth 103 and the toothpockets cut into the edge of the strip defining the break 104 of thepresent implant 100 are linearly spaced along the pre-deployed implantand are located at an edge formed by the intersection of the peripheraledge of the exterior 110 and the break or slit 104. The preferredembodiment maintains a constant distance “L” (FIG. 23) between eachtooth 103, and the tooth pockets defining teeth 103 are spaced halfwaybetween the locations of the bend relief geometry 102. This spacingensures that the deployed teeth 30, 103 will be in line with each otheras the spiral is wound around itself producing an un-aligned toothpattern 122 as shown in FIG. 23A.

Referring now to FIG. 23B thru 23D, an alternate spacing is depicted atL₁ thru L_(N) of the bend relief geometry 102 and teeth 103 that isbased on the arc length “L” of a polar spiral (T=a+bθ) given by theequation

$L = {\frac{1}{2}{b\left( {{\theta\sqrt{1 + \theta^{2}}} + {\ln\left( {\theta + \sqrt{1 + \theta^{2}}} \right)}} \right)}}$where θ is the angular dimension in radians between teeth 103 of a fullydeployed spiral 22. The length L₁ thru L_(N) between bend reliefgeometry 102 of an undeployed implant 100 will gradually increase fromthe proximal end 118 to the distal end 116. The location of the toothpockets defining teeth 103 will also follow the same equation, and willalways be spaced halfway between the bend relief geometry 102. Thisspacing ensures that the deployed teeth 30, 103 will be in line witheach other as the spiral is wound around itself producing an alignedtooth pattern 124 as shown in FIG. 23C.

It is preferred that the teeth 30, 103 and the bend relief areas 102 arespaced linearly, such that as the spiral is formed as seen in FIG. 23A,the teeth and bend relief areas end up in somewhat of a random pattern(this being one embodiment). If the above-listed equation is used(second embodiment), then the teeth 30, 103, as well as the bend reliefareas 102 will line up as the spiral takes shape as shown in 23C. Theteeth 30, 103 will line up along “tooth location lines” (FIGS. 23C and23D), and the bend relief areas 102 will line up along locations spacedat θ/2 (polar coordinates) or L/2 in linear dimensions. The distancedefined as L/2 (L₁/2, L₂/2 . . . . L_(N)/2) between the teeth 30, 103and the bend relief areas 102 ensures that the teeth will always bespaced halfway between the bend relief area as shown in FIGS. 23 thru23D. It is also preferred that this arrangement is created so that anytooth 20, 103 and bend relief area 102 are never aligned with eachother, resulting in a weakening of the structure. If L₁/2=0, then aspecific tooth 103 and bend relief area 102 would be aligned, and across-section taken perpendicular to that location would be relativelyweak.

Referring now to FIG. 19, bend relief features 102 are generallysemi-cylindrical or spherical concavities or dimples extending towardsthe interior and are formed from a portion of the exterior wall 110 ofthe pre-deployed implant 100. In the preferred embodiment, the bendrelief features 102 are created by forming a cylindrical or sphericaldimple or protrusion 126 that protrudes to the interior wall (FIG. 30).In essence, there should always be material, and never an opening in thecylinder wall where the bend relief features 102 are located. It iscontemplated that other shapes are also suitable, including but notlimited to oval, triangular, square, pentagonal, hexagonal and otherconfigurations of polygonal extruded shapes, both regular and irregular.

As seen in FIG. 17B, bend relief features 102 have a smaller crosssectional wall thickness “t” than the nominal implant wall thickness(“T”). This decreased wall section allows an easier bend transitionabout the axis of the semi-cylindrical or spherical concavities. Asidefrom the bend relief formations, it is preferred that the implant 100maintains a constant wall thickness “T” throughout the entire length.The process of bending the implant around itself and turning theinterior surface 112 towards the exterior of the implant 100 provides anactivation force for the shape memory materials.

Referring now to FIG. 24, it is also contemplated that the break or slit104 varies along the length of the pre-deployed implant 100, forming thelordotic or alternate profile 61 of surfaces 26 and 28 as illustrated inFIG. 12. The arcuate length of the break or slit 104 may vary along thelength and may also be symmetric or asymmetric about the axis ‘V’ of theimplant 100, causing surfaces 26 and 28 to have differing profiles 61.

Referring now to FIGS. 25 thru 32A, an implant delivery device isgenerally designated as 200. The delivery device 200 includes a deliverytube 201 which receives a fixed distal end deployment tip 202. At anopposite end, the delivery tube 201 is attached to a body collar 204 andthe collar is screwed into a housing 206. An implant loading chamber 208(FIG. 31) is located at an opposite end of the housing 206 from thedelivery tube 201, and is accessed thru a door 210 by pressing a doorrelease button 212. An implant tensioning cord 214 is preferablymanufactured from Sulene-PET (polyethylene-terephthalate) or similarmaterials and is fed thru a centerline of the delivery device 200defined by the delivery tube 201, and exits a distal end thru thedeployment tip 202. A distal end of the tensioning cord 214 is attachedto the delivery tube 201 creating the formation of a loop 216. Aproximal end of the tensioning cord 214 is wound around a cordtensioning knob 218 and can be controlled by a variable tensionadjustment mechanism 220.

Referring now to FIGS. 25, 29, 29A, 30, 32 and 32A, the implant 100 isloaded and oriented on rails 203 attached to the body collar 204 asshown in FIG. 29A. The purpose of the rails 203 is to orient thepre-deployed implant such that the break or slit 104 is facing downward.When a trigger 222 is pulled and released or the manual trigger override 224 is pushed forward and back, it actuates a trigger lever 226which is held in position by a return spring 229 and a center post 228.The trigger lever 226 actuates a trigger slide 230 into a double actingcam mechanism 232 causing a clockwise rotation of the mechanism as seenfrom above the housing 206 (FIG. 29) The trigger slide 230 has adouble-sided ramp 254 with an angled front surface 246 and an angledrear surface 248 (FIG. 32A).

When the trigger slide 230 moves forward, the angled front surface 246acts upon a front ramp 250 attached to the cam mechanism 232, causingrotation of the cam mechanism. When the trigger 222 is released, thetrigger slide 230 is forced backwards by the spring 229 and the triggerlever 226, causing the rear angled surface 248 to engage a rear ramp 252of the cam mechanism 232, also causing rotation in the clockwisedirection when viewed from the rear of the device as depicted in FIGS.32 and 32A. Thus, each depression and release of the trigger 222 causesa double actuation of the cam mechanism 232. The rotation of the cammechanism 232, through preferably frictional engagement between arelatively resilient ring 255 (FIGS. 29, 32 and 32A) and the Archimedesscrew 234, preferably made of a rigid material such as stainless steel,causes counter-clockwise rotation of the Archimedes screw (FIGS. 30 and32).

A reverse acting spline 236 which is a groove in the surface of thescrew 234 interfaces with the bend relief features 102 of the implant100, causing movement of the implant towards the distal end deploymenttip 202. Thus, with each retraction of the trigger 222, the implantstrip 100 is indexed towards the deployment tip 202. As seen in FIG. 28,the implant 100 rides within the tube 201 until it hits a flared ramp240, forcing the implant break or slit 104 to open as depicted in FIG.22 and change the concavity or arcuate cross-section of the implant 100.The implant 100 then hits the tensioning cord 214 and curls around theloop 216, creating the spiral shape 22. The trigger 222 is pulled andreleased until the implant 100 is fully deployed within the patient. Dueto the relative stiffness of the curled proximal end 118, the curledshape of the implant 100 is maintained, since the proximal end forms theoutermost surface of the implant and thus prevents uncoiling.Alternately, when shape memory polymers are used for the implant 100,the proximal end 118 has a memory of its curled shape and thus does notuncurl.

Referring now to FIG. 30, the tensioning cord 214 is cut post deploymentby pulling back on a cord release lever 242, causing a cord knife 244,which reciprocates within the delivery tube 201, to move in such amanner that a sharp edge 256 of the knife 244 retracts backwards andsevers the cord 214. The delivery device 200 can then be removed.

While a particular embodiment of the present in-situ formed spinalimplant has been shown and described, it will be appreciated by thoseskilled in the art that changes and modifications may be made theretowithout departing from the invention in its broader aspects and as setforth in the following claims.

What is claimed:
 1. A device for installing a coiled elongate strip as aspinal implant, comprising: a housing having a delivery tube at one end,and an implant loading chamber at an opposite end; an indexing mechanismwhich moves the strip from said loading chamber to said delivery tube; adeployment tip being disposed in operational relationship to an end ofsaid delivery tube, said deployment tip including a ramp for changingthe concavity of the strip; a tensioning cord disposed in operationalrelationship to said deployment tip and forming a loop for causing thestrip to form a coiled spiral upon progressive movement from saiddelivery tube; and, a splined screw rotating within said delivery tubefor advancing the strip toward said deployment tip upon actuation ofsaid trigger, wherein the elongate strip has a plurality of dimplesextending towards an inner surface of the implant, and said splinedscrew has a helical groove constructed and arranged for accommodatingthe dimples for moving the implant through the device.
 2. The device ofclaim 1 further comprising at least one rail disposed within saiddelivery tube and configured to orient the coiled elongated strip as thestrip is moved through said delivery tube.
 3. The device of claim 1wherein the ramp comprises a first arc lying in a first plane, and asecond arc lying in a second plane and being larger than said first arc,and said second arc disposed closer to said distal end than said firstarc, each of said first and second planes being perpendicular to alongitudinal axis of the delivery tube.
 4. A device for installing acoiled elongate strip as a spinal implant, comprising: a housing havinga delivery tube at one end, and an implant loading chamber at anopposite end; an indexing mechanism which moves the strip from saidloading chamber to said delivery tube; a deployment tip being disposedin operational relationship to an end of said delivery tube, saiddeployment tip including a flared ramp for changing the concavity of thestrip; a tensioning cord disposed in operational relationship to saiddeployment tip and forming a loop for causing the strip to form a coiledspiral upon progressive movement from said delivery tube, wherein theflared ramp comprises a first arc lying in a first plane and a secondarc lying in a second plane, said second arc being larger than saidfirst arc, and said second arc disposed closer to said distal end thansaid first arc, each of said first and second planes being perpendicularto a longitudinal axis of the delivery tube.
 5. The device of claim 4further comprising at least one rail disposed within said delivery tubeand configured to orient the coiled elongated strip as the strip ismoved through said delivery tube.
 6. The device of claim 4 furtherincluding a reciprocating knife disposed in said delivery tube and underoperator control for severing said tensioning cord upon placement ofsaid coiled implant.
 7. The device of claim 4 further including asplined screw rotating within said delivery tube for advancing the striptoward said deployment tip upon actuation of said trigger.
 8. The deviceof claim 7 wherein the elongate strip has a plurality of dimplesextending towards an inner surface of the implant, and said splinedscrew has a helical groove constructed and arranged for accommodatingthe dimples for moving the implant through the device.
 9. A device forinstalling a coiled elongate strip as a spinal implant, comprising: ahousing having a delivery tube at one end, and an implant loadingchamber at an opposite end; an indexing mechanism which moves the stripfrom said loading chamber to said delivery tube; a deployment tip beingdisposed in operational relationship to an end of said delivery tube,said deployment tip including a ramp for changing the concavity of thestrip; a screw within said delivery tube configured to rotate and movethe strip from said loading chamber to said deployment tip; a tensioningcord disposed in operational relationship to said deployment tip andforming a loop for causing the strip to form a coiled spiral uponprogressive movement from said delivery tube; and, at least one raildisposed within said delivery tube and configured to orient the coiledelongated strip around said screw as the strip is moved through saiddelivery tube.
 10. A device for installing a coiled elongate strip as aspinal implant, comprising: a housing having a delivery tube at one end,and an implant loading chamber at an opposite end; an indexing mechanismwhich moves the strip from said loading chamber to said delivery tube; adeployment tip being disposed in operational relationship to an end ofsaid delivery tube, said deployment tip including a ramp for changingthe concavity of the strip; a tensioning cord disposed in operationalrelationship to said deployment tip and forming a loop for causing thestrip to form a coiled spiral upon progressive movement from saiddelivery tube; and, a reciprocating knife disposed in said delivery tubeand under operator control for severing said tensioning cord uponplacement of said coiled implant.
 11. The device of claim 1 furtherincluding a splined screw rotating within said delivery tube foradvancing the strip toward said deployment tip upon actuation of saidtrigger.
 12. The device of claim 11 wherein the elongate strip has aplurality of dimples extending towards an inner surface of the implant,and said splined screw has a helical groove constructed and arranged foraccommodating the dimples for moving the implant through the device. 13.The device of claim 1 further comprising at least one rail disposedwithin said delivery tube and configured to orient the coiled elongatedstrip as the strip is moved through said delivery tube.